The invention relates to a fuel injection nozzle for gas turbine drives equipped with at least one heat exchanger for heating the combustion air, whereby the fuel injection nozzle presents an annular conduit that runs coaxially with reference to the longitudinal axis of the nozzle, which can be ventilated by coolant air that is not heated by the heat exchanger.
In gas turbine power plants with heat exchangers, it is frequently observed that the injection nozzles carbonize at the combustion chambers, which leads to a considerable disturbance in operation and even sometimes to engine breakdown. Disturbances of this nature are easy to get rid of, in principle, but depending upon design and construction, a considerable expenditure in time and effort sometimes has to be counted on. In heat exchanger gas turbines with annular reversing combustion chambers, it is customary for example to dispose the annular fuel conduit and the injection nozzles within the engine housing. Cleaning carbonized injection nozzles in this case would entail partial disassembly of the engine, which can practically never be done with built in gas turbines.
The carbonizing of the nozzles occurs from cracking processes, if the fuel in the nozzle system is heated beyond the characteristic temperature for the hydrocarbon in the fuel in question. Highest temperatures usually occur at the nozzle tips: heating occurs there through convection, and particularly from emission from the combustion chamber. For reasons that relate to strength, injection nozzles are generally made of heat-resistant materials which, as a rule, have a rather low coefficient of heat conduction. The result is that in the zones in which the heat occurs, there are localized high temperatures in structural parts, because the heat is not carried off quickly enough to cooler areas, or released to the fuel. This has the consequence that in the lower partial load range (small fuel throughput) and especially after the engine has been cut off (fuel throughput zero), there are conditions at the nozzle tips that crack the fuel, and the troubles that have been mentioned then occur.
The invention is intended to eliminate these drawbacks in the scope of the problem that has been described, and to produce an injection nozzle for gas turbine engines that will be broadly protected from direct impingement of heat and that can be deliberately cooled, whereby especially heat that occurs in the zone of the nozzle tip will be carried off as quickly as possible to cooler structural parts, or cooler engine areas.
To solve this problem according to a preferred embodiment of the invention, the combination of the following features is provided:
(a) The fuel injection nozzle is held in a structural part that in part constitutes the outer housing of the combustion chamber and is integrated in the engine housing, and from there it is taken via a bore in the back wall of the flame tube that receives the primary air supply, into the primary zone of the combustion chamber.
(b) The annular channel of the injection nozzle that can be impinged upon by cool air is disposed between an outer shielding wall and a sleeve-like central body for fuel supply, which is connected with the forward section of the annular channel by means of fuel supply bores in the injection head, and is also connected with the primary zone via intake openings in this region in the shielding wall.
(c) The central body for fuel supply bears exclusively on the outer shielding wall via contact surfaces disposed in the region of the outer housing of the combustion chamber, as well as in the zone of the injection head. The said shielding wall advantageously belongs to the fixed component of the nozzle body, in the region of the combustion chamber that is on the outside of the housing.
The invention otherwise is based on a known fuel injection nozzle as in German Auslegeschrift No. 2,036,756, with the intention of furnishing an advantageous further development of this known solution, especially in the matter of the mentioned invention.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention.